In order to produce monocrystalline ingots from polycrystalline ingots, the polycrystalline ingots are broken up into fragments of about 100 mm diameter. These fragments are used to fill a crucible in Czochralski crystal pulling (CZ crystal pulling). Since the surface of the ingots varies in roughness at different positions, the breaking gives rise to fragments which have these rough surface portions. At present, the parts with, for example, cracks, protrusions (popcorn), craters (verbal classification) etc. are manually sorted out by trained personnel before they reach the crucible for CZ crystal pulling, because this defective material causes quality reductions in the method there.